Rotary hinge assemblies which connect a vehicle door to a vehicle body are commonly equipped with a rotary damper in order to enable the vehicle door to open and close smoothly. The rotary damper generally includes a fluid filled chamber and a connecting pin rotatably supported in the chamber for rotation with respect to the chamber. One end of the pin is disposed inside the chamber and is connected to a vane which undergoes rotational movement inside the chamber, while the other end of the pin is connected to the vehicle door. The other end of the pin is connected to the vehicle door in such a way that the vane is able to gain rotational movement within the chamber in response to opening and closing of the vehicle door.
Further, when the vehicle door is opened or closed, the vane in the chamber rotates against a rotational resistance applied by the fluid present in the chamber. Such rotational resistance applied by the fluid attenuates the rotational movement of the vane or the vehicle door in order to enable the vehicle door to open and close smoothly.
An exemplary rotary damper is described in U.S. Pat. Nos. 9,027,979 and 7,243,398 which describe a rotary damper employed in a hinge of a vehicle door. The rotary damper includes a fluid filled chamber and a vane connected to the vehicle door. Such fluid filled chamber includes a fluid channel or constricted section through which the fluid has to pass, during the rotational movement of the vane in the chamber, in response to opening and closing of the vehicle door. During the passing of the fluid through the constricted section, the constricted section produces a resistive force against the rotation of the vane or the vehicle door, in order to enable the vehicle door to open and close smoothly.
However, while application of the resistive force against the rotational movement of the vehicle door is performed using the rotary damper described in the aforementioned patents, end users including driver and passengers of the vehicle may be deprived of any option of controlling the resistive force as per their requirement.